The present invention relates to a method for the use of dihyrochalcone derivatives and specifically phlorizin and derivatives thereof to block the intestinal absorption of glucose and renal tubule resorption of glucose in mammals and thereby provides a method for the treatment of obesity and diabetes.
It is known that the subcutaneous administration of phlorizin causes inhibition of the sugar transport process through intestinal and renal cell walls in mammals and thereby decreases the level of glucose in the bloodstream and promotes the excretion of glucose (e.g., Journal of Clinical Investigation, 79, p. 1510 (1987), ibid., 80, 1037, (1987), ibid., 87, p.561 (1990). Specifically, phlorizin is known to inhibit the sodium glucose symporter, an enzyme transport system found in the small intestine that is used to transport glucose across intestinal epithelium, and in the renal tubule, where the enzyme transports sodium, lithium and glucose from the tubule into the renal vasculature. By blocking the action of this enzyme, phlorizin prevents intestinal absorption of glucose and the renal resorption of glucose. Consequently dihydrochalcones, such as phlorizin, can be used to reduce obesity and lower the intake of insulin in diabetic mammals.
It has also been stated in a number of publication that the oral administration of phlorizin, although effective as glucose transport inhibitor through intestinal and kidney cells, is not useful because toxic effects, which are in part attributed to the formation of phloretin, the hydrolysis product of phlorizin in the intestines. As a result a number of phlorizin and phloretin derivatives have been developed which have been asserted as avoiding the toxic effect of particularly phloretin (U.S. Pat. Nos. 4,760,135, 5,731,292 and 5,767,094).
It is an object of the present invention to provide a method for the oral administration of dihydrochalcones to inhibit the renal tubular glucose absorption, and/or inhibit the absorption of glucose at the intestine, under conditions, which reduce the formation of toxic byproducts. It is another object to provide a method to block the postprandial rise in blood glucose. Another object is to provide a method for the treatment of acute glucose toxicity and to correct hyperglycemia. The present invention also provides a method for blocking the uptake of glycosylated drugs and hormones into cells and to increase their renal excretion. It also involves a method to increase sodium and lithium excretion from the body as a method for the treatment of lithium toxicity. It has also been discovered that dihydrochalcone derivatives are useful in preventing hypoglycemia. Additionally the present invention provides a weight loss method.
These and other objects are accomplished by orally administering a dihydrochalcone derivative in multidoses on a daily basis at a time when the intestine is relatively uninvolved in the digestion of food. The dihydrochalcones preferably used are phlorizin and derivatives of phlorizin which inhibit the transfer of glucose through the walls of intestinal and renal cells.
The present invention comprises orally administering dihydrochalcone derivatives to mammals on a daily multidose basis at a time when the intestinal tract of the mammal is at a low point in its gastric activity, e.g. on an empty stomach. The dihydrochalcone derivatives employed in the present invention include specifically phlorizin and derivatives of phlorizin which are able to inhibit the transfer of glucose. The number of doses administered and the amount of the dihydrochalcone derivative in each dose will of course vary with the mammal, the derivative and the effect desired, but should be at least three times daily and should contain at least 10 mg/kg of body weight. Similarly the optimum time to administer the derivative will vary but preferably is 90 to 30 minutes before food is consumed assuming regular dietary habits. The actual conditions and concentrations under which the derivative is administered can be best established experimentally by measuring the increase in the glucose content in urine or the decrease of glucose in the blood stream after having established the desired degree of inhibition.
The preferred dihydrochalcone compounds employed in the procedure of the present invention are dihydrochalcone glycosides such as phlorizin and alkoxy, alkyl- and aryl amine substituted phlorizins where the substituents can be either on the glycoside moiety or on the dihydrochalcone moiety, provided not more than one hydroxyl group in the dihydrochalcone moiety and not more than two hydroxyl groups in the glycoside moiety have been replaced by the stated substituents. In general the procedure of the present invention is most effective with phlorizin itself although improved blocking of glucose transport is also obtained with other phlorizin derivatives using the procedure of the present invention.
Phlorizin itself is a well-known pharmaceutical ingredient that is obtained from the bark of apple trees. Although it has been known to be useful, particularly through subcutaneous administration, as a method to study the cellular transport of glucose, it has not found acceptance because of the belief that phlorizin exhibits toxic side effects. As a result derivatives of phlorizin have been developed which are asserted not to exhibit such side effects, e.g., U.S. Pat. Nos. 4,760,135, 5,767,094 and 5,731,292. However, these derivatives are not seen to be totally satisfactory when used under the conditions described in the literature. The present invention is based on the discovery that the oral administration of phlorizin on an empty stomach allows the use of lower concentrations of phlorizin at levels which do not appear to have a toxic effect on the operation of key organs such as the pancreas or brain, which is indicative of toxic effects on the mammal as a whole. Although I do not wish to be bound by such it is my belief that the reason for the ability to use phlorizin without toxic side effect is the ability to reduce the hydrolysis of the phlorizin to a minimum.
The dihydrochalcone glycosides employed in the present invention may be administered in dry powder, tablet, capsule or aqueous or other suitable form. The material however should not be ingested with food products, which stimulate gastric activity or compete with phlorizin for intestinal absorption. The dose will vary depending on the conditions of patients and the severity of the condition to be ameliorated. The phlorizin compound should be administered at least three times daily and not more than five times to coincide with conditions of low gastric and intestinal activity. The amount of the phlorizin compound in each dose should be at least 10 mg/kg of body weight. It can be increased but should not exceed 50 mg/kg of body weight in order to avoid toxic effects.